The invention relates to a method for calibrating sensors in drilling equipment provided with a movable carrier, a frame mounted to turn about a horizontal axis that is transverse to the direction of movement of the carrier, and an upper carriage mounted to the frame to turn about a vertical axis, and an angle sensor for measuring a turning angle of the upper carriage in relation to the frame and gravity-based sensors for measuring inclination of the upper carriage. The invention further relates to an arrangement for calibrating sensors in a drilling equipment provided with a movable carrier, a frame, a boom assembly mounted to turn about a turning axis vertical to the frame, an angle sensor for measuring a turning angle of the boom assembly in relation to the frame, and gravity-based inclination sensors mounted to the boom assembly and rotating with the assembly about the turning axis for measuring inclination in the direction of two co-ordinate axes that are perpendicular to each other.
Different kinds of measuring devices and/or sensors are used on movable drilling equipment for desired orientation and positioning of the drill rod and the drill hole formed with it. Such measuring devices are typically gravitation-based inclination sensors and sensors indicating movements of different movable parts. Typical examples include angle sensors of joints and distance or motion sensors indicating linear movement. Likewise, measuring devices indicating compass direction or those based on satellite navigation are used for measuring a compass direction and location of the drilling equipment in a global coordinate system.
A simple measuring device, such as one indicating drill rod inclination, may be calibrated in a simple manner by using only a few tools, such as a spirit level or a similar device, to turn the drill rod to a vertical position. In that case the display of the measuring device shows sensor errors. More complicated measuring devices are often provided with a plural number of sensors to measure a plural number of directions and angles, and therefore they are not very easy to calibrate.
Today devices are typically calibrated in a factory environment, where a sufficient number of different reference devices are available and different inclined planes, points with known locations and other necessary devices or means may be provided for the calibration. In that case, there are also persons available who are well versed in calibration and able to use the devices and means.
A problem with current calibration methods is lack of measuring devices or an environment unsuitable for calibration or the fact that the device to be calibrated must often be transported to the measuring site for calibration. This causes both loss of time and costs. Moreover, if for any reason there is need to check the calibration of the device, this cannot be done quickly on site, but a large amount of measuring devices and other equipment must be transported to the location. This may also cause measurement and calibration errors due to poor conditions.